About the Four Types of Fossil Fuels

About the Four Types of Fossil Fuels
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With the 21st century edging into third decade, few terms in the everyday English language are more loaded or contentious than fossil fuel.

The U.S. alone consumes about a million kilojoules (kJ) of energy per person per day. In order for the world to meet the energy demands inherent in a global civilization dependent on galactic amounts of fuel for transportation, electricity production, home and commercial use, and industrial applications, a correspondingly rich source of energy is required.

As of 2019, fossil fuels – petroleum, coal and natural gas, with production a fourth type having ceased in 2006 – provided the majority of this energy. Despite the controversies over their impact and the intense effort to develop alternatives to fossil fuels (i.e., "clean" energy, much of it in the form of "renewables"), these fuels changed the world almost overnight and remain indispensable today, however uncomfortably.

About the Name "Fossil Fuel"

All fossil fuels in existence were produced over a long time period from the remains of plants and animals that lived millions of years ago. The slow transformation of this carbon-heavy material into various hydrocarbon compounds resulted in the creation of plentiful, highly flammable fuels.

But to call these fuels the products of fossils is incorrect. Fossils – which represent the impressions of old life forms, not their remains – are also extraordinarily old, but this is about all they have in common with fossil fuels. The underlying connotation that these fuels might be in some way precious, though, is on target.

Overview of the Four Fossil Fuels

The four types of fossil fuels are petroleum, coal, natural gas and Orimulsion (capitalized because it is a proprietary, or trade, name). They have a number of important physical, chemical and other properties in common, but perhaps the most critical fact about fossil fuels is that they are not renewable. Once they are used up, that's it; many more millions of years have to pass before even small amounts can be made again, assuming the same processes will ever even occur on the same scale.

Also, fossil fuels in their natural form store tremendous amounts of carbon, keeping it from leaking into the atmosphere. Burning them, however, "unlocks" the carbon and returns it to the atmosphere at rates far faster than even would occur without human industry in the mix. The combustion of fossil fuels plays an established role in the anthropogenic global warming (AGW) that has been underway for decades and is already damaging ecosystems around the planet.


In the year 2017, petroleum – in other words, crude oil and substances known as "natural gas plant liquids" – accounted for 28 percent of American primary energy production. The U.S., while perhaps regarded by many of its own citizens as mainly an oil-importing nation, is actually among the top oil producers in the world. Thanks to the reputation of some Middle Eastern nations as effectively controlling most of the world's oil production, and to undeniably sky-high U.S. oil consumption, this fact is often obscured.

Because the petroleum product gasoline is relatively portable compared to coal, most petroleum production and use is in the transportation sector. In fact, 71 percent of energy used in the U.S. transportation sector is supplied by petroleum, which plays virtually no role in the generation of electrical power.

  • In 2018, over half of U.S. oil produced came from two states alone: Texas and North Dakota.


Coal supplied about 18 percent of U.S. energy needs in 2017. The total amount produced was 775 million short tons, and this coal came from a total of 24 U.S. states. Wyoming by far contributed the greatest share at 41 percent, with West Virginia a distant second at 12 percent. A decade earlier, coal's contribution to American energy production was just slightly lower than that of natural gas, 23 percent to 22 percent.

The solid nature of coal makes it ideally suited for keeping in one place for electricity production, and this has been its overwhelming role in the energy game over the years. Coal production in 2017 was about the same as it was in 1979, but the U.S. population also grew by about 100 million people in that time. As coal production for electricity has dropped in favor of other sources, coal's overall role in the fuel economy has diminished.

Coal is about 70 to 90 percent carbon by mass. Four subtypes exist, all with different properties in terms the amount of energy liberated from the breaking of carbon bonds when the coal is burned.

Natural Gas

Natural gas accounted for 32 percent of the American energy share in 2017, and total production was the second-highest ever. In fact, beginning in about 2005, natural gas became more accessible in much of the United States thanks to the increased use of horizontal drilling and the well-stimulation technique known as hydraulic fracturing ("fracking").

The rise of fracking in the early 21st century – a practice controversial because it consumes vast amounts of water, invariably disturbs the local environment and may even have the potential to cause small earthquakes – is tied to the decision on the part of a Texas oil company to try to extract natural gas from a kind of rock called shale, abundant in that part of the country. The commercial success of the technique led to its adoption by other companies in other areas where shale is found.

  • Natural gas is considered clean-burning compared to other fossil fuels; it is getting it out of the ground that is the most problematic aspect of its production.

Orimulsion: A Flash in the Energy Pan

Off the coast of Venezuela sits the Orinoco Oil Belt, which is home to a unique repository of an especially heavy type of oil. Starting in 1991, this was made into a proprietary product called Orimulsion, which consisted of 70 percent heavy oil and 30 percent water. It was hoped that this could cut significantly into the fossil-fuel market share, but production was stopped in 2006.

As of 2016, some 1.2 trillion barrels' worth of Orimulsion-ready oil was believed to still be sitting in the Orinoco Oil Belt.

Fossil Fuels vs. Renewable Energy Sources

By the early 2000s, the term "renewables" has become just as much of a friendly term in environmental circles as "fossil fuels" had become an unwanted guest. As a result, renewables and nuclear power (considered "clean," but a source of energy with many detractors) accounted for 23 percent of U.S. energy in 2017.

But fossil fuels, despite occasional dire predictions about flagging underground stores, are in no danger of running out anytime soon even at current levels of use. Unless policies radically change, fossil fuels are expected to still account for 78 percent of energy used worldwide in 2040. This might actually be a bad thing for Earth as a whole as it fails to fully force humanity to cohesively pursue a workable and sustainable energy agenda that both meets global power needs while permitting the avoidance of a global-warming disaster.

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